Tissue Cassette Dispensing Apparatus

ABSTRACT

The present invention aims to provide a dispensing apparatus for dispensing individual tissue cassettes from a stack of cassettes, the apparatus includes a hopper for receiving a stack of tissue cassettes, the hopper having an aperture through which cassettes are dispensable; ejection means for ejecting a cassette through the aperture; and retention means for retaining all but one of the cassettes in the stack as an individual cassette is ejected.

This application is a continuation of application Ser. No. 12/234,062,filed Sep. 19, 2008, now pending.

The present invention relates to tissue cassettes and to an apparatusand method for dispensing such tissue cassettes.

Tissue cassettes are small trays used for holding samples of tissue foranalysis. Typically the tissue is human tissue (although it may beanimal tissue) which may have been taken from a patient for the purposesof performing analysis or diagnostic tests. Generally, tissue cassettesare made of plastic and are a standard rectangular size of approximately3 cm by 2 cm wide and approximately ½ cm deep.

Clearly tissue cassettes need to be labelled accurately e.g. withidentification details (such as relating to the patient). This can bedone by hand but there are also existing tissue cassette processingmachines which are used to process and label large numbers of cassettes.One such machine (sold under the brand name Shandon Microwriter™)includes several hoppers. Each hopper is adapted to receive a stack oftissue cassettes and the machine has a dispensing mechanism forextracting cassettes from a hopper one at a time. Successive hoppers canbe moved into position with respect to the mechanism so that cassettescan be removed from different hoppers, as required.

Cassettes are manufactured by many different manufacturers and whilstthey are typically of the size and shape described above, the cassettesof different manufacturers do differ slightly in detail. However,generally users expect to be able to use cassettes produced by differentmanufacturers with a single machine. This can lead to problems inreliably dispensing cassettes from the hoppers since the hoppers are notnecessarily designed to accommodate all types of cassettes. Thereforeone typical problem is that on occasion the dispensing mechanism canbecome jammed.

Generally, a number of cassettes (typically 25 or 50 or 75) are suppliedloaded inside a tube and it is this tube which is loaded into a hopper.The hopper is therefore appropriately sized to receive the tube but thisleads to the problem that as a cassette leaves the tube the dimensionsof the hopper are such that it is not held firmly within the hopper.This can lead to some variation in alignment within the hopper of acassette which is about to be dispensed by the dispensing mechanism,which in turn increases the likelihood of possible problems such asjamming the dispensing mechanism.

Accordingly, the present invention aims to provide a tissue cassettedispensing apparatus and method which reduces some or all of theseproblems.

At its most general level, the dispensing mechanism of the hopper of thepresent invention does not rely on the cassettes stacks beingself-supporting during dispensing unlike the prior art equipment.Instead, the present invention, in one aspect, incorporates means forholding all but one of the stack of cassettes in position as a singlecassette is dispensed, so that the remainder of the cassette stack doesnot interfere with the dispensing mechanism.

Additionally or alternatively, also at a general level, the presentinvention tackles the second problem mentioned above in a further aspectwhich is to provide means within the hopper for retaining a cassette orcassettes in a suitable alignment position once the cassette(s) has beenremoved from its storage tube.

Accordingly, in a first aspect, the present invention providesdispensing apparatus for dispensing individual tissue cassettes from astack of such cassettes, the apparatus including:

a hopper for receiving a stack of tissue cassettes, the hopper having anaperture through which cassettes are dispensable;

ejection means for ejecting a cassette through the aperture;

retention means for retaining all but one of the cassettes in the stackas an individual cassette is ejected.

In this way, as mentioned previously, the retention means prevents orreduces interference in the ejection process by the remaining cassettestack.

Preferably, the ejection means includes a tray in which a single tissuecassette may be held. The tray is moveable so as to be useable totransport a tissue cassette away from the stack of cassettes when acassette is to be dispensed. Preferably, the tray is arranged such that,in normal use, a cassette may slide out of the tray under the action ofgravity alone.

The hopper may be such that part of it is adapted to receive a tubeinside which the cassettes are supplied. Part or most of the tube maythen extend out of the hopper.

Preferably the hopper includes a pocket in which at least part of thestack of cassettes may be held in use. Preferably the retention meansacts on one or more of the cassettes in the pocket. More preferably, theretention means acts on at least the lowest cassette in the pocket whichwhen it is retained in position in the pocket by the retention meansthen in turn serves to hold the remainder of the cassettes in the stackin position. If the injection means incorporates a tray, the lowestcassette in the pocket will typically be the cassette next in the stackto the cassette in the tray.

In some embodiments, the retention means includes a finger or toothwhich is moveable so as to grip a cassette, possibly e.g. by holding itagainst one or more of the walls of the pocket or hopper.

Preferably the hopper also includes gate means for closing the aperture.Such gate means act to prevent unwanted dispensing of a cassette. Thegate means are openable so as to permit a cassette to be ejected throughthe aperture. Preferably the gate means are biased to a closed position.

Preferably the retention means is arranged in conjunction with the gatemeans such that when the gate means is fully open (i.e. opensufficiently to permit ejection of a cassette) the retention means is inoperation to retain the remainder of the cassettes in the stack. Morepreferably, the opening of the gate means causes the retention means tooperate as described. Preferably when the gate means is fully closed,the retention means is not operating i.e. is not retaining the cassettesin the stack in any particular position. In the example given abovewhere the retention means includes a finger or tooth, preferably thegate means includes a member which causes the finger/tooth to engage oneor more cassettes in the stack as previously described.

In the embodiments of the apparatus in which the ejection means includesa tray, the gate means may act so as to prevent a cassette from leavingthe tray until/unless the gate means is fully open. In the example wherethe tray is slideable so as to transport a cassette within the tray awayfrom the stack, the sliding action of the tray may open the gate means.Preferably this is accomplished simply by the tray bearing on the gatemeans and pushing the gate means open. In this way, the gate meansprogressively opens as the tray slides.

Preferably the action of the tray on the gate in turn causes the gate tooperate the retention means as previously described. However,additionally or alternatively, the movement of the tray may be arrangedto trigger the operation of the retention means independently of theopening of the gate means. Preferably this would achieve the sameresult, namely that the retention means is activated so as to retain thecassettes in the stack before the gate means is fully open so as topermit release of a cassette from the tray.

So, in one embodiment, the sequential operation of the apparatus will beas follows:

-   1. A plurality of cassettes are loaded into the hopper. If the    cassettes are supplied in a cassette tube, then part of the cassette    tube may be inserted into a portion of the hopper so that cassettes    can exit from the tube into the pocket, preferably under the action    of gravity alone.-   2. The lowermost cassette in the stack exits from the pocket to a    location where it may be acted upon by the ejection means. That    location may be a tray.-   3. When it is wished to dispense a cassette, the ejection means acts    so as to move a single cassette away from the stack. This may be by    movement of the tray.-   4. Before the cassette being dispensed is fully dispensed, the    retention means acts so as to retain the remainder of the cassettes    in the stack so as to reduce any interference by the remaining stack    on the dispensing operation. This may be activated by operation of    the gate means, which in turn activates the retention means, which    acts e.g. on the lowest remaining cassette in the stack.-   5. Once the dispensing operation is completed, the retention means    releases the cassette(s) which were being held in position, so as to    permit the next cassette in the stack to move into the position in    which it can subsequently be acted on by the ejection means. In one    example, this is achieved by the tray being returned to its rest    position, which in turn permits the gate means to close which in    turn permits the retention means to release the cassette previously    retained. The whole remaining stack then moves downwards.

As previously mentioned, the rejection means may include a tray. Thetray may further include separation means for improving the separationof the cassette held within the tray from the adjacent cassette (i.e.the next lowest cassette in the stack) as the tray is moved. This helpsprevent the problem mentioned previously whereby two cassettes areattempted to be dispensed together, causing a jam. Such separation meansmay be achieved by suitable sizing and/or shaping of one or more sidewalls of the tray. In particular, the rear wall of the tray (i.e. thewall opposite the end of the tray from which a cassette is removablefrom the tray) may be suitably sized and/or shaped. In particular, therear wall may be angled with respect to the rear edge of a cassette(when in position in the tray) so that a first upper portion of the rearwall i.e. a portion distant from the base of the tray) is nearer to thecassette than the lower edge of the rear wall. This helps to grip thecassette in position. The upper portion referred to may be the upperedge of the rear wall of the tray. Alternatively, it may be an area ofthe rear wall between its upper and lower edges.

Additionally or alternatively, a second upper portion of the rear wallof the tray may be angled in the opposite direction i.e. angled so thatthe lower part of that upper portion is nearer to the cassette in thetray than another part of that upper portion. This then acts as a wedge,so as to lift the adjacent cassette in the stack away from the cassettein the tray as the tray moves. This second upper portion may be furtherfrom the base of the tray than the first upper portion, if both areincluded.

As mentioned previously, the present invention has a second aspect whichaddresses the problem of the cassettes not being retained accurately inposition in the hopper once the cassettes have been removed from acassette tube.

Accordingly, in a second aspect, the present invention providesdispensing apparatus for dispensing individual tissue cassettes from astack of such cassettes, the apparatus including:

-   -   a hopper for receiving a stack of tissue cassettes, the hopper        having an aperture through which cassettes are dispensable;    -   ejection means for ejecting a cassette through the aperture;    -   the hopper including a pocket for receiving part of the stack of        cassettes;    -   whereby at least one wall of the pocket is provided with holding        means for retaining one or more cassettes in a desired position.

Preferably the holding means protrude away from the wall of the pocketso as to constrict the available space for the cassette(s)between thepocket walls. Preferably a pair of opposing side walls of the pocket areprovided with holding means. In one example, such holding means consistof protuberances, preferably opposing protuberances.

Practically, the side walls of the hopper may be dimensioned so as to besuited to receive a cassette tube as previously mentioned. The sidewalls of the hopper may also include one or more protuberances so as togrip the cassette tube more effectively. Preferably the side walls ofthe pocket are in line with the side walls of the hopper and the holdingmeans project further away from the side walls of the pocket than eitherthe side walls of the hopper or any protuberances on the side walls ofthe hopper. This serves to ensure that the cassettes are better held inposition once they exist from the cassette tube. By contrast, forexample, if the side walls of the hopper and pocket (and anyprotuberances) were dimensioned the same, then clearly if the dimensionis sufficient to hold the cassette tube tightly it will be too large tohold the cassettes equally tightly once they have existed from thecassette tube.

Preferably there is a gap between any protuberances on the side wall(s)of the hopper intended to be adjacent the tube in use and the holdingmeans, i.e. the distances between opposite side walls at this gap isgreater than the distance between opposite protuberances. Preferablythis gap is located so that it is adjacent the lower end of a cassettetube when a cassette tube is located in the hopper. The reason for thisis that sometimes the lower end of a cassette tube is slightlycompressed which can inhibit the removal of cassettes from the tube. Theinclusion of this gap enables the lower end of the cassette tube toexpand more freely, making it easier for cassettes to exit.

The first and second aspects of the present invention may be usedtogether or separately. In addition, in a further aspect, the presentinvention relates to a tissue cassette processing apparatus. The tissuecassette processing apparatus includes at least one dispensing apparatusaccording to either or both of the first and second aspects of thepresent invention. In practice, the tissue cassette processing apparatusmay include a plurality of dispensing apparatuses, typically between 2and 12, preferably between 4 and 8 and most preferably 6.

The tissue cassette processing apparatus may include ejection operatingmeans for operating the ejection means of a dispensing apparatus. Suchejection operation means may be controlled (e.g. computer controlled) tooperate the ejection means when required.

Additionally, the tissue cassette processing apparatus may includetransport means for transporting either or both of the ejectionoperation means and the dispensing apparatus(es) in relation to eachother. In one embodiment, the ejection operation means may remainstationary and the plurality of dispensing apparatuses are moveable inrelation to the ejection operation means. For example, the plurality ofdispensing apparatuses may be arranged on a carousel, so that thecarousel can be rotated by the transport means so that the ejectionoperation means can operate on any of the dispensing apparatuses in turnas required.

Preferably the dispensing apparatus(es) is/are removably mounted in thetissue cassette processing apparatus. More preferably, each dispensingapparatus is removable even when it contains a whole or partial stack oftissue cassettes and preferably the whole or partial stack of tissuecassettes are retained in the hopper e.g. by the gate means. In thisway, different dispensing apparatuses can be introduced to or removedfrom the tissue cassette processing apparatus part way throughprocessing.

In a further aspect, the present invention also provides a method ofoperating a dispensing apparatus and/or a cassette processing apparatusin accordance with any one or all of the features described above.

Embodiments of the present invention will now be described by way ofexample, with reference to the accompany drawings in which:

FIG. 1 shows a dispensing apparatus incorporating aspects of the presentinvention;

FIG. 2 shows a bottom view of the dispensing apparatus of FIG. 1;

FIG. 3 shows a side view of the dispensing apparatus of FIG. 1;

FIG. 4 shows a view of the dispensing apparatus of FIG. 1 with the traypartially slid out;

FIGS. 5 to 8 show a cross-sectional side view through the dispensingapparatus of FIG. 1-4 with the progressive operation of the apparatusillustrated;

FIG. 9 a shows a view of the dispensing apparatus as seen in FIG. 8, butwith a cassette tube in place;

FIG. 9 b is a detail from FIG. 9 a showing the tray;

FIG. 10 is another view of the apparatus as seen in FIG. 8 but with apartially empty cassette tube in place;

FIG. 11 is a general perspective view of the tissue cassette processingapparatus of FIG. 9;

FIG. 12 shows a partial sectional view through a tissue cassetteprocessing apparatus incorporation aspects of the present invention,including incorporating the dispensing apparatus of FIGS. 1-8.

FIG. 1 shows a perspective view of a dispensing apparatus incorporatingaspects of the present invention. The dispensing apparatus, which istypical referred to generally as a “cassette hopper”, is indicated bynumeral 2. The apparatus includes a hopper 4 for receiving a stack oftissue cassettes. Typically the cassettes will be supplied inside acassette tube, and the hopper 4 includes side walls 6, 8 which aremutually dimensioned and located so as to receive the cassette tube. Theside walls 6, 8 include protuberances 10, 12 (in this view suchprotuberances can only be seen on sidewall 8, but similar protuberancesmay also be included on the inner side of sidewall 6) to help hold thecassette tube more firmly in position.

The dispensing apparatus also includes an aperture through whichcassettes are dispensable and, in this view, the aperture is closed by adoor or gate 14.

FIG. 2 is a view of the bottom of the dispensing apparatus of FIG. 1 andshows an engagement member 16 which is part of the ejection means forejecting a cassette though the aperture. The engagement member 16 canalso be seen clearly in FIG. 3.

As can be seen in FIG. 4, the ejection means also includes a tray 18which, in this example, is slideably mounted so as to be moveable toprotrude or partially protrude from the dispensing apparatus. The tray18 is operably connected to the engagement member 16 such that movementof the engagement member 16 moves the tray. In addition, as seen in FIG.4, movement of the tray also pushes on the door 14 causing the door 14to open.

In one aspect of the invention, the dispensing apparatus of FIGS. 1-4 isincorporated into a tissue cassette processing apparatus as shown inFIG. 11. The tissue cassette processing apparatus includes a carousel 20onto which a plurality of dispensing apparatuses may be mounted. In FIG.11, only one dispensing apparatus is shown mounted, but the particularcarousel shown has the capacity to hold up to six such dispensingapparatuses. The carousel 20 is moveable (e.g. rotatable) so as to beuseable to locate each dispensing apparatus in a desired position asrequired. The tissue cassette processing apparatus may include one ormore ejector operator means(and typically may include only one ejectoroperator means) which is useable to eject a cassette from a dispensingapparatus by operating the ejecting means of that dispensing apparatus.This will be described in more detail with reference to FIG. 12 once theoperation of a single dispensing apparatus has been described. Thecarousel 20 is operable by indexing means or transport means so as tolocate a desired dispensing apparatus in the correct position so thatthe transport mechanism is useable with respect to that dispensingapparatus.

FIGS. 5-8 show a sectional view through the dispensing apparatus ofFIGS. 1-4, illustrating the sequential operation of the dispensingapparatus.

In FIG. 5, the dispensing apparatus is in the “rest” or “closed”position. In this position, the dispensing apparatus may be separatefrom a tissue cassette processing apparatus, and is in a suitable stateto be removed from or introduced into e.g. the carousel of a tissuecassette processing apparatus. In FIG. 5, the presence of any tissuecassette tube has been omitted for clarity, but the position of such atube (when used) can be seen in FIGS. 9 a and 10 later.

FIG. 5 clearly shows the tray 18 connected to the engagement member 16.The tray includes a base 30 and an end wall 32. A stack of fourcassettes 40, 42, 44, and 48 can be seen in FIG. 5. The lowest cassette40 is located in the tray 18 and, in this state, the remainder of thecassettes rest on the lowest cassette 40.

In FIG. 5, the door 14 is in the closed position. The door 14 isarranged to be rotatable around pivot 50 but other mechanisms foroperating the door may be envisaged. The door 14 may be biased to aclosed position by biasing means (not shown) e.g. a spring.

In addition, the door is operably connected to the rotation means. Inthis example, this is achieved by door 14 including a bearing member 52which is operably connected to a finger 60. The finger 60 is rotatablearound pivot 62 and includes a tooth 64 which is moveable into and outof engagement with at least one of the cassettes in the stack. In thisexample, the engagement is with cassette 42 i.e. the cassette which isadjacent the cassette located in the tray 18. Also in this example thetooth 64 is moved into and out of engagement by rotation of the finger64 around the pivot 62, but other mechanisms for achieving this are ofcourse envisaged.

FIG. 6 shows the state of the dispensing apparatus 2 when the cassette40 has begun to be dispensed. The engagement member 16 has been moved bye.g. the transport means of a tissue cassette processing apparatus andthis has caused the tray 18 to slide down to the left as seen in FIG. 6.The rear wall 32 of the tray 18 bears on rear corner 70 of cassette 40located in the tray so as to begin to slide cassette 40 away from therest of the stack of cassettes 42-48. A front edge 34 of tray 18 bearson door 14 so as to begin to open door 14. In turn, the bearing member52 bears on finger 60 which begins to rotate as previously described.

FIG. 7 then shows the state when the retention means of the dispensingapparatus has engaged but in which the cassette has not yet beendispensed. As can be seen, the tray 18 has slid further out of thehopper 4 which has caused door 14 to open yet further, but not quite yetfar enough to permit cassette 40 to slide out of tray 18 under theaction of gravity. However, door 14 has been moved far enough such thatbearing member 52 has operated finger 60 sufficiently to engage tooth 64with a first portion (e.g. front edge 72) of cassette 42. The action oftooth 64 presses a second portion (e.g. rear portion 74) of cassette 42against part of the hopper so as to ensure that cassette 42 remains inthe hopper. This also helps reduce the pressure of cassette 42 oncassette 40, ensuring the smooth dispensing of cassette 40.

In FIG. 8, the dispensing apparatus is in the state in which cassette 40is ready to dispense. The tray 18 has been moved far enough (e.g. to itsmaximum extent out of the hopper) to fully open door 14. This means thatcassette 40 is free to slide out of tray 18 e.g. under the action ofgravity. Typically the cassette being dispensed will slide into aportion of a cassette processing apparatus for further processing. Inaddition, as can be seen in FIG. 8, the tooth 64 is still engagingcassette 42 so as to retain it in position even though it is no longersupported at all by cassette 40. Optionally, to further help support thenow lowest cassette 42 in the stack, the tray is operably connected to arear support member 80. As can be seen in the sequence of FIGS. 5-8, therear support member 80 moves progressively with the tray 18 so as tosupport the rear underside of cassette 42 as cassette 40 progressivelymoves out from under cassette 42.

As will be readily appreciated, once cassette 40 has been dispensed, thesequence shown in FIGS. 5-8 may then be reversed. In other words, tray18 is withdrawn back into the hopper by the movement of engagementmember 16. This progressively allows door 14 to close (e.g. under theaction of its biasing means) which progressively releases the retentionmeans on cassette 42. Once the retention means has been completelyreleased, tray 18 will be back in the rest position and cassette 42 isthen free to drop into tray 18 (e.g. under the action of gravity) andthe apparatus is ready to repeat the process again.

FIG. 9 a shows a sectional view to a dispensing apparatus in a similarstate to that of FIG. 8 i.e. with the tray 18 fully extended. However,in FIG. 9 a the apparatus is shown with a tissue cassette tube 90 inplace. Also more cassettes (in this case 10) are shown remaining in thestack whilst a cassette is being dispensed. As previously explained,typically the cassettes are supplied in a cassette tube 90 and it isconvenient simply to load the entire tube 90 into the hopper of theapparatus. However, the cassette tube 90 does not extend all the way tothe bottom of the hopper, as can be seen in FIG. 10. Instead, thecassettes emerge from the lower end of the cassette tube 90 (e.g. underthe action of gravity) into a pocket region 100 of the hopper, in thiscase at the lower end of the hopper.

As previously mentioned, the upper walls of the hopper are provided withprotuberances 10, 12 (in this example, each item 10 and 12 consists of apair of protuberances but any suitable number may be used). Theseprotuberances serve to locate the cassette tube 90 in position and tohold it firmly. However, protuberances 10, 12 do not extend all the waydown the side walls of the hopper continuously. Instead, in a region 102adjacent the end of the cassette tube 90, the protuberances are reducedor even omitted altogether. As previously explained, this helps topermit the sides of the cassette tube 90 at its end to flex more easilyand therefore to allow the cassettes to exit the tube 90.

The pocket region 100 of the hopper also includes protuberances. In FIG.10, only part of protuberances 110 can be seen on one of the side wallsof the pocket region. These protuberances can also be seen more clearlyin FIGS. 5-9. However, in some embodiments, the side wall of the pocketregion will include two protuberances, or even two pairs ofprotuberances, in a similar fashion to items 10 and 12 of the hopper. Inaddition, the opposite side wall of the hopper and/or pocket region mayinclude similar side protuberances (not seen). Again, as previouslyexplained, the protuberances 110 of the pocket region serve to hold thecassettes in the correct position once they have emerged or partiallyemerged from the tube 90. In order to accomplish this, in someembodiments, protuberances 110 may extend further away from the sidewall of the pocket region than the similar protuberances 10, 12 extendfrom the side wall of the hopper.

FIG. 9 b shows a sectional view of the portion of the tray 18. Thisillustrates more clearly the nature of the rear wall 32 of the tray. Inparticular, according to one aspect of the invention, the inner face 33of the rear wall 32 is not perpendicular to the base 30 of the tray.Preferably, a portion of it is inclined to the base at an acute angle,and in this example the angle shown is 86 degrees. However, that may bevaried to e.g. between 80 and 89 degrees. The purpose of this is to helpto grip the rear portion 74 of cassette 40 in the tray, to help preventcassette 40 from lifting upwards out of the tray.

One optional additional feature of rear wall 32 of the tray 18 is that asecond portion(the upper part 35) of inner face 33 may be angled in theopposite direction to the remainder of the inner face i.e. is at anobtuse angle to the base 30. If, in spite of the other features of thepresent invention, the rear of adjacent cassette 42 should drop down asthe tray is being slid forward, then this upper portion 35 helps to pushcassette 42 back into position, and away from cassette 40.

FIG. 12 shows a sectional view though part of the tissue cassetteprocessing apparatus of FIG. 11. This illustrates an ejection operationmechanism (generally 200) for operating the ejection means of adispensing apparatus as previously described. It also shows an indexingmechanism (generally 210) (transport means) for operating the carousel20 so as to bring a desired dispensing apparatus into the appropriateposition so that a desired cassette can be dispensed. Ejection operationmechanism 200 includes a finger 202 which engages with engagement member16 and is usable to move engagement member 16 to slide the tray ofdispensing apparatus to as previously described.

The invention may include any variations, modifications and alternativeapplications of the above embodiments, as would be readily apparent tothe skilled person without departing from the scope of the presentinvention in any of its aspects.

1. A dispensing apparatus for dispensing individual tissue cassettesfrom a stack of such cassettes, the apparatus including: a hopper forreceiving a stack of tissue cassettes, the hopper having an aperturethrough which cassettes are dispensable; ejection means for ejecting alowermost one of the cassettes through the aperture; retention means forretaining all but the lowermost one of the cassettes in the stack as thelowermost cassette is ejected, the retention means including a supportmember that acts to support at least part of the weight of the stack asthe lowermost cassette is ejected, the retention means thereby reducingthe force exerted on the lowermost cassette by the weight of the stackas the lowermost cassette is ejected; the ejection means including atray in which the lowermost tissue cassette may be held.
 2. A dispensingapparatus according to claim 1 wherein the tray is moveable so as to beuseable to transport a lowermost cassette away from the stack ofcassettes when a lowermost cassette is to be dispensed.
 3. A dispensingapparatus according to claim 1 wherein the hopper includes a pocketregion in which at least part of the stack of cassettes may be held inuse.
 4. A dispensing apparatus according to claim 3 wherein the supportmember of the retention means acts on one or more of the cassettes inthe stack in the pocket region.
 5. A dispensing apparatus according toclaim 4 wherein the support member of the retention means acts on atleast the lowest cassette in the pocket region, which when the at leastthe lowest cassette in the pocket region is retained in position in thepocket region by the retention means, then the at least the lowestcassette in the pocket region in turn serves to hold the remainder ofthe cassettes in the stack in position.
 6. A dispensing apparatusaccording to claim 5 wherein the lowest cassette in the pocket region isthe cassette next in the stack to the cassette in the tray.
 7. Adispensing apparatus according to claim 1 wherein the retention meansincludes a finger or tooth which is moveable so as to grip a cassette.8. A dispensing apparatus according to claim 1 wherein the hopperincludes gate means for closing the aperture.
 9. A dispensing apparatusaccording to claim 8 wherein the gate means are biased to a closedposition.
 10. A dispensing apparatus according to claim 8 wherein theretention means is arranged in conjunction with the gate means such thatwhen the gate means is fully open the retention means is in operation toretain the remainder of the cassettes in the stack.
 11. A dispensingapparatus according to claim 10 wherein the opening of the gate meanscauses the retention means to operate.
 12. A dispensing apparatusaccording to claim 10 wherein when the gate means is fully closed, theretention means is not retaining the cassettes in the stack in anyparticular position.
 13. A dispensing apparatus according to claim 10wherein the gate means includes a member which causes the finger ortooth to engage one or more cassettes in the stack.
 14. A dispensingapparatus according to claim 8 wherein the gate means acts so as toprevent a cassette from leaving the tray unless the gate means is fullyopen.
 15. A dispensing apparatus according to claim 1 wherein the trayincludes separation means for improving the separation of the lowermostcassette held within the tray from an adjacent cassette as the tray ismoved.
 16. A dispensing apparatus according to claim 15 wherein a rearwall of the tray is angled with respect to a rear edge of a lowermostcassette, when the lowermost cassette is in position in the tray, sothat a first upper portion of the rear wall is nearer to the lowermostcassette than a lower edge of the rear wall.
 17. A dispensing apparatusaccording to claim 16 wherein a second upper portion of the rear wall ofthe tray is angled so that a lower part of the second upper portion isnearer to the lowermost cassette in the tray than another part of thesecond upper portion.
 18. A tissue cassette processing apparatusincluding: at least one dispensing apparatus according to claims 1, andan ejection operating means for operating the ejection means of adispensing apparatus.
 19. A tissue cassette processing apparatusaccording to claim 18 further including transport means for transportingeither or both of the ejection operating means and the dispensingapparatus(es) in relation to each other.
 20. A dispensing apparatus fordispensing individual tissue cassettes from a stack of such cassettes,the apparatus including: a hopper for receiving a stack of tissuecassettes, the hopper having an aperture through which cassettes aredispensable; ejection means for ejecting a lowermost one of thecassettes through the aperture; the hopper including a pocket region forreceiving part of the stack of cassettes; whereby at least one wall ofthe pocket region is provided with holding means for retaining one ormore cassettes in a desired position, the holding means including two ormore protuberances that protrude away from one or more walls of thepocket region so as to constrict the available space for a cassettebetween the walls of the pocket region.
 21. A dispensing apparatusaccording to claim 20 wherein the side walls of the hopper include oneor more protuberances so as to grip the cassette tube more effectively.22. A dispensing apparatus according to claim 21 wherein the side wallsof the pocket region are in line with the side walls of the hopper andthe holding means project further away from the side walls of the pocketregion than either the side walls of the hopper or any protuberances onthe side walls of the hopper.
 23. A method of operating a dispensingapparatus for dispensing individual cassettes from a stack of suchcassettes, the method including the steps of: loading a stack ofcassettes into a hopper; exiting the lowermost cassette in the stackfrom a pocket region of the hopper to a location where the lowermostcassette may be acted upon by ejection means that includes a tray inwhich the lowermost cassette may be held; with the ejection means,ejecting the single lowermost cassette held in the tray of the ejectionmeans away from the stack; and before the lowermost cassette beingejected is fully ejected, retaining with a retention means a remainderof the cassettes in the stack so as to reduce any interference by theremaining stack on the ejecting step of the lowermost cassette, theretaining step including the step of supporting with a support member ofthe retention means at least part of the weight of the stack as thelowermost cassette is ejected, the retention means thereby reducing theforce exerted on the lowermost cassette by the weight of the stack asthe lowermost cassette is ejected.